More than one-third of the world population is infected with Mycobacterium tuberculosis, the bacterium that causes the Tuberculosis (TB) disease. Each year, 8 million people become infected with TB, and 2 million people die from the disease. TB significantly affects developing countries and is also becoming an increasing problem in developed areas of the world.
Persons infected with TB can be asymptomatic for a considerable period of time, and can be in a latent stage of the disease. In its active state, the disease is often manifested with an acute inflammation of the lungs, resulting in fever and a nonproductive cough. If untreated, serious complications and death typically result. Present diagnostic assays are often inaccurate, and are unable to distinguish between persons in the latent stage of the disease and those in the active stage.
Currently, vaccination with live bacteria is one method for immunizing persons against the disease. However, TB vaccination with certain live bacteria has often been the source of controversy in some countries, including the United States, and consequently has not been put into widespread use in the U.S. Additionally, current diagnostic tests are many times unable to distinguish between persons who have been immunized, and persons infected with TB.
Effective vaccination and accurate early diagnosis of the disease are important to control the disease. Consequently, a need exists for effective diagnostic assays that detect active infection by the TB bacteria. A further need exits for a vaccine that does not use a live bacteria and provides a protective immunogenic response to the disease.